Web bending fixture

ABSTRACT

A web bending fixture to bend lithographic plates used in web offset printing and production. Precise bends are created by a precision machine tool fixture. The fixture utilizes continuously supported eccentric camming members, one on each end of the fixture, each supported by a plurality of split bearings within which the camming members rotate. After the lithographic plate is precisely aligned with unique registration means and immobilized, the camming members, are moved into position and, rotating within the bearings, form the leading and trailing edges of the plate around precisely positioned and fixed anvils.

BACKGROUND OF THE INVENTION

Web offset printing and production requires precision bending oflithographic plates to assure precise alignment of the images on theplates and longevity of the plates. Plate runs can vary betweentwenty-five thousand to one million impressions without platemalfunction, depending in substantial part on the preparation andbending of the plate. Common problems with plates attributable to theweb bending fixture utilized include plates with edges that are bent toosharply, not allowing the plate to seat naturally on the cylinder lips,plates with edges which are not bent sharply enough to fit the cylinderlips, plates which do not have parallel leading and trailing edge bends,plates that are out of register because not properly aligned prior tobending or not properly immobilized during bending, and plate lengthsbetween bends which are too long or too short for the cylinder or plateshaving bent edges which are too long or too short for the cylinderbecause the plates were improperly positioned on the bender beforebending.

Since the plate must conform precisely to the press cylinder on which itis to be utilized these problems cause the plate to be deformed whenprinting takes place and causes metal fatigue, normally in the area ofthe bends in the plate, which eventually leads to flexing, stress andeventual cracking of the plate. The actual physical formation of thebends in the plate is also of extreme importance because bendingmechanisms which distort the metal when bending cause stress and stressfractures in the bend which substantially shortens the printing life ofthe plate. Imprecise bends, such as bends which are not straight, alsolead to flexing of the plate during printing which substantiallyshortens the plate life.

Inventive activity has been directed to the bending of lithographicplates, most of which has incrementally improved various aspects ofbending of such plates. For example, very precise bends have beenachieved with bending fixtures employing the principles of a brake presswhere the material is clamped before bending and a bar or plate forms aprecise bend at the edge of the clamp. Brake press bending, however,distorts and stretches the metal and changes the metal structureresulting in varying thicknesses of metal in the bend causing fracturesand stress at the bend which shortens plate life. Other attempts havebeen made to resiliently form the metal around the edge of the anvilwith the use of compression or tension springs. However, such springsare normally more resilient than the metal being bent and imprecisebending of the edges can occur, particularly in view of the bendingpressures applied.

SUMMARY OF THE PRESENT INVENTION

The present invention incorporates an overall system approach to offsetprinting and as an element of that system the precision machine tool ofthe instant invention has been created to precisely position and bend alithographic plate in precise alignment with previous and subsequentplates.

The invention incorporates mechanical and operational strengths toaccomplish the objectives of the invention at a very high level ofperformance. The advantages of the invention include interrelated andinterconnected mass structure that assures a solid, long termrelationship of all components.

The anvils around which bends are formed are structurally andmechanically fixed to assure precise positioning of the bends on theplate. Bends in the plate are created by rolling the metal around anvilsutilizing eccentric camming members which are supported throughout theirlength by a plurality of split bearings which provide a control of thebending operation far more effectively than conventional resilientfree-bending devices.

Pursuant to the system approach there is a continuity of control fromstripping to plate making in conjunction with which the plates to bebent are prepunched with a precision register punch to assure that theimage registration is exact before the plate is bent. The plate isinserted onto the bed of the invention and rides on an air cushiongenerated through the bed. The plate is first positioned with limitswitches and thereafter aligned with registration pins to assure properregistration of the plate and image after the bend has been completed.The registration pins perfectly align the image on the plate relative tothe bends to be formed in the plate.

Air pressure through the table is then reversed to create a vacuumhold-down pressure. After the vacuum has been created and the plateimmobilized the register pins are withdrawn from the plate and aclamping bar is applied to each end of the plate to further immobilizeit and hold it precisely in position when the bend is created.

With the plate so positioned eccentric camming members preciselypositioned to accommodate the radius of the anvil around which the bendis to be formed and the exact thickness of the metal or stock to bebent, rolls the metal around the anvil to form the bend. This assures auniform thickness of metal throughout the bend without stress.

Each eccentric camming member is fully supported throughout its lengthby a plurality of split bearings to assure straightness of the bend andparallelism of the bends on the leading edge and trailing edge of theplate and alignment of the image to each bend.

The camming member is then reversed, a retractable anvil is withdrawnand the upper half of the bearings are raised so that the plate can beremoved from the fixture without force or stress of any kind on theformed plate.

Use of this precision fixture thus produces the highest qualitylithographic plate, ideally suited for the cylinder of the offset presson which the plate is to be run, the plate being capable of reproducinghundreds of thousands of impressions without costly cracking and theconcomitant down time of the press that a cracked plate inherentlycauses.

It is therefore an object of the invention to provide a metal formingaction and bending of a lithographic plate that eliminates cracking andbreaking of plates on web offset presses.

It is an objective of the invention to provide a metal forming actionwhich causes a minimum destruction of metal structure eliminating stresspoints and creating a uniform and maximum thickness of metal over theentire length of bends with a minimum distortion of the metal duringbending.

It is an objective of the invention to create maximum straightness ofbend along the entire length of bends formed on the fixture.

It is an object of the invention to create a controlled radius of bendto permit the closet possible relationship of radius of bend of theplate to the dimensions of the cylinder upon which the plate is to beused.

It is an objective of the invention to produce parallelization ofleading and trailing edge bends and parallelization of leading andtrailing edge bends with the print line of the image to be reproduced.

It is an objective of the invention to control the tolerance dimensionbetween the leading and trailing edge bends to assure properrelationship of the plate to the cylinder upon which the plate is to beused.

It is an objective of the invention to control the register of image tothe bends of the plate to prevent cocked plate problems.

These and other features and objectives of the present invention will beapparent from a consideration of the accompanying description, drawingsand claims.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a pictorial perspective view of the invention taken from thefront right corner and slightly above the fixture with the eccentriccamming members in the raised or "ready" position.

FIG. 2 is a pictorial perspective view of the fixture of FIG. 1 takenfrom the rear left and slightly above the fixture with the eccentriccamming members in the down "clamp" and "bend" position.

FIG. 3 is a plan view of the invention from above showing the pluralityof bearings which support each camming member and the location of limitswitches and registration pin mechanisms to position and align the platebefore bending.

FIG. 4 is an enlarged partial pictorial detail view in perspective takenat 4 of FIG. 3 showing one of the registration pin mechanisms withassociated limit switch used for alignment of the plate to assurepreciseness in positioning of the bends and the image to be reproduced.

FIG. 5 is an enlarged partial pictorial detail view in perspective takenat 5 of FIG. 3 showing additional structure and operation of theregistration pin mechanism of FIG. 4.

FIG. 6 is a partial elevational view of the registration pin mechanismof FIG. 4 and associated cylinder taken along the line 6--6 of FIG. 3.

FIG. 7 is a partial sectional elevation of the machine taken along theline 7--7 of FIG. 1 with the eccentric camming members in the raisedposition.

FIG. 8 is a partial sectional elevation of the invention taken along theline 7--7 of FIG. 1 with the eccentric camming members in a down clampand bend position.

FIG. 9 is the same view as FIGS. 7 and 8 with the eccentric cammingmembers in a rotated bend position.

FIG. 10 is the same view as FIGS. 7 through 9 with the eccentric cammingmembers in a raised position and with the retraction anvil retracted toallow removal of the bent lithographic plate.

FIG. 11 is a sectional detail view in elevation taken along the line11--11 of FIG. 1 to show the structure and operation of the retractableanvil.

FIG. 12 is a partial elevational view of one of the four actuator sets,this view being the right front actuator set as shown in FIG. 1 with allelements in a raised "ready" position similar to that shown in FIG. 7.

FIG. 13 is a partial elevational view of the right front actuator set ofFIG. 12 in the clamping position corresponding to FIG. 8.

FIG. 14 is a partial elevational view of the right front actuator set ofFIG. 12 in a rotated bend position corresponding to FIG. 9.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The web bending fixture 20 of the instant invention is designed for usein web offset printing and production and is particularly advantageousas part of a register control system to create repetitive impressions ofimages properly positioned on the paper being utilized.

The ability to properly register plates on press cylinders with aminimum of deviation accomplishes two major advantages; a minimum lossof productive press time, and a major reduction in costly paper wastage.

Register control should begin in preparatory procedures and continue tothe pins 22 in the web bending fixture 20 of the instant invention. Thecontrol should begin with the punching of holes in stripping materialsand in the edge of the lithographic plates 24 to be utilized. Properregistration procedures should be pursued in the stripping operationwith plate frame exposure of plates 24 and in the operation known in theart as the "step and repeat" operation. These are the operations thatprovide the exact placement of images on the lithographic plates 24.They are of little value, however, if the control of register does notcontinue during the bending of the plates 24 to fit them on the presscylinder.

The bending of plates 24 to close tolerances requires strength andweight of the bending fixture 20. The weight of the structural elementsassures a constant relationship of components and years of productionwithout undue wear. FIGS. 1, 2 and 3 give a perspective overview of theinvention. A support table 26 is provided created of heavy structuralsteel fixedly secured together such as by welding to provide a solidsupport for the bending fixture 20. A shelf 28 is conveniently providedfor, in this embodiment, a vacuum pump and valving for an air logicsystem. Also conveniently connected to the support table is a controlpanel 30 and, on the other end of the table 26, shown in FIG. 2, acontrol box 32.

Control of the registration and bending operation is, in the preferredembodiment shown, automated with an air logic system controlling thesequential functions of the bending operation. It should be obvious thateach step in the operation can be achieved manually with the inventionas shown in the drawings. Those skilled in the art will realize thatcontrol of the bending fixture 20 may also be accomplished with otherpneumatic controls, hydraulics or electronically with a printed circuitboard or the like. The preferred embodiment uses air because ofcleanliness of operation, ease and simplicity of maintenance and theability to achieve rapid and inexpensive repairs if needed. Use of airalso permits the use of NFPA interchangeable air cylinders forpositioning, registration, clamping, bending and kick-out. This allowsand permits the use of any other NFPA designated cylinder when acylinder is in need of replacement which further eases themaintainability of the fixture 20.

All operating controls for the fixture 20 are preferably located on thecontrol panel 30. Preferably the register cycle and the forming cycle,to be discussed below, are controlled by individual push buttons 32, 34,and a red "stop" button 36 is also included. Key control 39 can beprovided to selectively choose automatic operation or, if preferred,manual operation, or the control panel 30 can conveniently providemanual operation only.

The basic operative elements of the invention 20 which cooperatestogether to provide a lithographic plate 24 ready for use on thecylinder of a web offset press are generally shown in FIGS. 1 through 3and shown in detail in the remaining figures. The bed 40 of the fixture20 upon which the plate 24 rests during bending is provided with ahardened anvil 42, 44 on each end, one of which 44 is retractable asshown in FIGS. 7 through 11 for removal of the plate 24 after it isbent. An air duct 50 is provided through the bed 40 which initiallycreates, through apertures 54, an air cushion upon which the plate 24rides for purposes of positioning and thereafter a vacuum is created toproduce a vacuum hold down feature through the apertures 54 in the bed40.

Plates to be bent are positioned and aligned in registration with theuse of limit switches and registration pins 22. Registration holes 27 inthe plate 24 are to assure that the image position is in register withthe bends. In some cases the bends are not to be exactly parallel to theedge of the plate 24. Thus, the plate 24 is positioned relative to theregistration pins 22 with limit switches and the registration pins 22automatically position the floating plate 24 on the bed 40 so that thebends, the print line and the image will be in exact register when bent.

Since the anvils 42, 44 are the object of all forming pressures, toassure accuracy in making the hundreds of thousands of bends ofconventional aluminum plates, and stainless steel when required, theanvils 42, 44 are hardened. The anvils 42, 44 utilize a ground radiuswith tolerance controlled, in the preferred embodiment, to ±0.003 of aninch. This accuracy meets fully the tolerances required for properbending of plates 24 in normal situations.

The eccentric camming members 60, 62 which roll the bends around theanvils 42, 44 are also machined to exact tolerances and hardened. Eachcamming member 60, 62 is rotatably secured at each end within fulloilite bearings 61 in steel end plates 70, 72 and 74, 76 and botheccentric camming members 60, 62 are also fully supported throughout bya plurality of split bearings 80. As shown in FIGS. 1-3, six splitbearings 82, 84, 86, 88, 90, 92 and 94, 96, 98, 100, 102, 104 areemployed intermediate the ends of each camming member 60 and 62respectively. It has been found advantageous to use four to six bearings80 depending on the size of the plates 24 to be formed and for thelargest plates 24 additional bearings 80 can be used and, in addition,additional reinforcement (not shown) can be employed in the center ofthe camming members 60, 62.

As shown in FIGS. 7 through 10, each of the plurality of split bearings80 consist of a split oilite bearing surface 110, 112 each portionsupported in an upper and lower bearing mount 114, 116 respectively. Thelower bearing mounts 116 are fully integrated into the solid steel table26, 40 of which the anvils 42, 44 are a part. The upper bearing mounts114 slidably engage the lower bearing mounts 116 so that when bendingpressures are applied there is no slippage or movement of the bearingmounts relative to each other. Strength of the upper bearing mounts 114are assured by securing them to solid steel header bars 113, 115spanning the end plates 70, 74 and 72, 76 and if further strength isnecessary the upper surface of the header bars 113, 115 lend themselvesto the use of a bolster bar (not shown) which can use gussets (notshown) along its length if additional strength is desired.

After the plate 24 is precisely aligned as will be described in moredetail below, the plate 24 is immobilized by vacuum and by clampingmembers 120, 122 which engage the plate 24 upon activation of a firstset of four cylinders 130, 132, 134, 136 operatively connected to theend plates 70, 72, 74, 76 to slide them in associated slide assemblies140, 142, 144, 146. Thereafter the eccentric camming members 60, 62 arerotated with the use of four sets 150, 152, 154, 156 of rack 170, 172,174, 176 and pinion gears 160, 162, 164, 166, one set for each eccentriccamming member 60, 62, with one pinion on each end of both eccentriccamming members 60, 62. Rotation of the pinion gears 160, 162, 164, 166is accomplished with the use of the corresponding racks 170, 172, 174,176 which one slidably engaged in slide assemblies 180, 182, 184, 186associated with each end plate 70, 72, 74, 76 to move downward from theup or "ready" position and each actuated by a corresponding cylinder190, 192, 194, 196.

In view of the use of air for all movement in the system automatedlubrication can be achieved in the air filter operation wheremicroscopic drops of oil can be picked up and circulated through thesystem as air enters the system. Air filters also remove moisture fromthe air stream which could be damaging to the system. To the extentpossible, oilite bearings are used throughout the fixture 20 which areself-lubricating surfaces that resist wear and require no furtherlubrication.

Operation of the bending fixture 20 can best be understood withreference to FIGS. 7 through 10 and FIGS. 12 through 14 which detail theoperational steps and the cooperation of the structural elements of theinvention.

Operation of the web bending fixture 20 is preferably accomplished inthree cycles, the register cycle during which the plate 24 is preciselyaligned on the fixture 20, the forming cycle during which the plate 24is precisely bent to fit the press cylinder, and a reversing cycle afterwhich the plate 24 can be easily withdrawn from the bender 20.

The register cycle is preferably actuated with a first control button 32which positions the retractable anvil 44 and causes an upward flow ofair through the same apertures 54 that are employed during vacuum holddown of the plate 24. The retractable anvil 44 is positioned with theuse of three cylinders 191 spaced along the anvil 44 each connected toan anvil cam 193 which moves upward to position the anvil 44 in theproper bend position and downward so the anvil 44 retracts. The anvil 44is slidably mounted in the bed 40 and interconnected therewith by aplurality of bolts 195 biased by springs 197 to retract the anvil 44when the cams 193 are withdrawn. Stability of the anvil 44 duringbending is assured by a plurality of bolts 203 secured in the bed 40 theheads 205 of which are contained by bolt slots 207 which also limitlateral travel of the anvil 44. The inclined surface 209 of the cam 193assures a precise control of anvil 44 travel, when properly adjusted,for placement of the bends and distance between the bends. The upwardflow of air through the bed 40 permits floating the plate 24 onto andinto the bending fixture 20 and is particularly advantageous whenplacing large plates 24 on the fixture 20 and has further value in theease with which the plate 24 responds to alignment and registrationprior to bending.

Positioning of the plate 24 prior to registration without visual effortresults from the use of three limit switches 202, 204, 206 shown in FIG.3. Two of the limit switches 202, 204 are cooperatively attached to theregistration pin mechanisms 208, 210 as shown in FIGS. 3 and 4 and thethird limit switch 206 is preferably positioned to engage a lateral sideof the plate 24 as shown in FIG. 3. The three point triangulationassures a precise alignment of the plate 24 for insertion of theregistration pins 22. In the preferred embodiment full contact must beestablished with all three limit switches 202, 204, 206 prior toregistration. To be certain the plate 24 is firmly held in exactposition a two second dwell time is preferably required before theregistration pins 22 move upward.

When plate 24 contact is confirmed by the limit switches 202, 204, 206the air logic system of the invention moves the registration pins 22upward with air cylinders 25. The structural and operational detail ofone 210 of the registration pin assemblies 208, 210, 212 is shown inFIGS. 4 through 6. The assembly 210, as shown, consists of theregistration pin cylinder 25, which moves the pin 22 through theprepunched hole 27 in the plate 24. Straddling the pin 22 and 27 areslidably mounted containment fingers 21, 23 to prevent the plate fromrising and to assure penetration of the pins 22 into the holes 27. Asnoted above it is the registration pins 22 which exactly align the plate24 prior to bending so that the image is in perfect registration whenused on the cylinder of the press. As shown best in FIG. 4, theincreasing diameter of the rounded tip of the pins 22 incrementallymoves the plate 24 into such exact alignment for perfect registration.The upward flow of air during this operation assures fast and easymovement of the plate 24 in gaining register control with the pins 22due to the lack of surface tension between plate 24 and bed 40.

During the forming cycle, as will be discussed below, portions of theregistration pin assemblies 208, 210 and 212 are moved out of the areaof the bends.

In most instances two registration pin assemblies 208, 210 can beutilized, as shown in FIG. 2, to achieve lateral and longitudinalalignment since the outer diameter of the registration pins 22correspond exactly to the inner diameter of the registration holes 27.Even more precise tolerance and alignment can be achieved with a thirdregistration pin mechanism 212 as shown in FIGS. 1 and 3 wheretriangulation of the positioning assures absolute alignment of the plate24 prior to bending.

A forming cycle is then initiated. The flow of air through the apertures54 of the bed 40 is reversed to create a vacuum pressure to hold theplate 24 flat and firmly to the bed 40 of the bender 20. It is preferredthat a sensor (not shown) be used to regulate the vacuum whereby noforming action can continue until the desired vacuum is drawn.

When the plate 24 is immobilized in a vacuum hold the registration pins22 are automatically withdrawn from the plate 24 by registration pincylinders 25 and the relative position of the structural elementsnecessary for bending are in the "ready" position shown in FIGS. 7 and12.

Each of the four clamping cylinders 130, 132, 134, 136 are thenactivated to bring down the spring loaded clamping bars 120, 122, oneach end of the fixture 20. In this manner, the plate 24 is completelyimmobilized and solidly held during the bending operation. Since thebending cylinders 190, 192, 194, 196 are mounted on the end plates 70,72, 74, 76 slidably mounted in the slide assemblies 140, 142, 144, 146retraction of the shafts of the slide cylinders 130, 132, 134, 136brings the eccentric bending members 60, 62 into position to bend asshown in FIGS. 8 and 13.

Referring to FIGS. 4 and 5 it can be seen how downward movement of theend plates 70, 72, 74 and 76 and associated header bars 113, 115 removesthe registration pin mechanism containment fingers 21, 23 from the areaof the bend. Integrally formed with the fingers 21, 23 is a rampmechanism 211 channeled and positioned to receive a positioning member213 solidly attached to the header bar 113. The positioning member 213,as shown, is a solid steel triangular finger 215 insertable in thechanneled ramp 211. The fingers 21, 23 and ramp 211 are slidably mountedin a registration pin assembly block 219 which is fixed to the bed 40.Thus, downward movement of the header bar 113 and 115 causes the fingers21, 23 to retract so that the metal 24 can be formed. As shown in FIGS.4 and 5 the ramp 211 and finger assembly 21, 23 of each registration pinmechanism 208, 210, 212 is biased by a spring 233 to return the fingers21, 22 and associated ramp 211 to a receiving position when the headerbar 113, 115 is raised to form a new plate 24.

Returning again to FIGS. 8 and 13 and the forming cycle, with eachcamming member 60, 62 held solidly against the upper split bearings 114constant alignment of each camming member 60 and 62 is assured by itspressure against the upper bearing surfaces 110 of the plurality ofsplit bearings 80 with which it is associated. The steel support beams,the header bars 113, 115 serve to hold the upper slit bearings 114 inexact and constant alignment. The camming member rotation cylinders, orbending cylinders 190, 192, 194, 196, two sets at the ends of bothleading and trailing edges of the plate 24, are actuated to form thebends. The shafts of the bending cylinders 190, 192, 194, 196 areconnected to racks 170, 172, 174, 176, slidably mounted in slideassemblies 180, 182, 184, 186 secured to the end plates 70, 72, 74, 76to rotate pinion gears 160, 162, 164, 166, one at each end of botheccentric camming members 60, 62.

As shown in FIGS. 8 and 13, the internal surface 220 of each cam 60, 62is, when forming begins, in contact with the upper surface of the plate24 which establishes the radius of rotation of each eccentric cammingmember 60, 62 as the radius of the anvil 42, 44 plus the thickness ofthe stock 24 being bent. At this point the split bearings surfaces 110,112 are in full contact with each other and the bearing mounts 114, 116are locked together by the support heel 225 on the lower split bearingmount 116 as shown in FIGS. 8 and 13. The result is perfect alignment ofthe split bearings 123, 125.

As each camming member 60, 62 is rotated around its respective anvil 42,44 the metal thickness across the entire bend remains uniform becausethe fully supported camming members 60, 62 can provide only a perfectlystraightline pressure and because the camming action is controlledprecisely on the radius of the anvil 42, 44 but separated from the anvil42, 44 by the thickness of the plate 24 being formed. This result isachieved by the alignment of the split bearings 123, 125 to provide aconstant pressure at various points along the camming member 60, 62 andthe plurality of split bearings 80 further establish a constantrelationship of each bending member 60, 62 to its respective anvil 42,44.

It is the constant relationship of the bending member 60 or 62 to theanvil 42 or 44 that improves the forming of metal. The use of the splitbearings 80 provides the constant bearing surface 110, 112 whichcontrols the alignment of the bending member 60, 62 relative to theplate 24 and the anvil 42, 44.

The radius of revolution of the camming members 60, 62 matches the innerradius of the split bearings 80. Thus a constant pressure is maintainedby the camming member 60, 62 against the inner surfaces 110, 112 toassure straightness in bending and the upper and lower split bearingsurfaces 110, 112 are in continuous contact during the bending operationto provide an extremely strong resistance to any deviation of thebending member 60, 62 during bending.

Further, precise control is achieved by precisely positioning thebending surface 220 of camming members 60, 62 away from the anvil 42, 44to compensate for metal thickness. Maintaining this distance of the flatportion 220 of the eccentric camming member 60, 62 to the upper surfaceof the plate 24 assures a radius of rotation of the bending surfaceclosest to the anvil and around the anvil to be equivalent to the radiusof the anvil 42, 44 plus the thickness of the stock 24. The clearance ofthe camming member 60, 62 to the anvil 42, 44 is controllable to ±0.001of an inch. In addition, if there is a substantial deviation in platethickness the web bending fixture 20 of the instant invention may beeasily modified by simply replacing the eccentric bending member 60 and62 with equivalent members 60', 62' having bending surfaces 220, 230machined to offset the necessary thickness.

In this manner the metal of the plate 24 is rolled or formed around theanvil 42, 44 radius without distortion, stretching or otherwisestressing the metal 24 in the bend and the plate 24 when used on acylinder will have a uniform thickness throughout the plate 24,including a uniform metal thickness throughout the bends.

After the plate 24 has been formed a reversing cycle is employed tocause reversal of the bending operation. As shown in FIG. 10, theeccentric camming members 60, 62 are rotated upward and the upper splitbearings 114 are raised. The anvil 44 is retracted with the use of threeretractable cams 193 activated by the cam cylinders 191 so that theplate 24 need not be forced off the anvil 42, 44. As shown in FIG. 11and previously described the retraction anvil 44 is spring biased withsprings 197 to retract the anvil 44 when the anvil cams 193 arewithdrawn. An automatic eject mechanism 240 is also convenientlyprovided as shown in FIGS. 2 and 3 consisting of an eject bar 242activated by two cylinders 244, 246 which slide the plate 24 off the bed40. At this point the plate 24 is perfectly formed, is not subject toany pressures and can be easily withdrawn from the bending fixture 20through apertures 270, 272 provided in the end plates 70, 72 for thispurpose.

In summary, operation of the fixture 20 is as follows: an air cushion isestablished through apertures 54 in the bed 40, and the retractableanvil 44 is positioned at the proper position for the bend which hasbeen previously established according to the thickness of the plate 24to be bent and the desired distance between bends. The plate 24 isplaced on the bed 40 and moved to three limit switches 202, 204, 206.Contact by the plate 24 with all three limit switches 202, 204, 206causes registration pins 22 associated with two 208, 210 or three 208,210, 212 registration pin mechanisms to exactly align the plate 24.

Forming of the plate 24 then takes place providing the plate 24 has beenproperly positioned with the register pins 22. The air cushion iswithdrawn and a vacuum is established. When the vacuum is establishedthe registration pins 22 are withdrawn and the four slide cylinders 130,132, 134, 136 go down to further immobilize and clamp 120, 122 the plate24 in position for the bend.

When the slide cylinders 130, 132, 134, 136 are down the four cylinders190, 192, 194, 196 associated with the eccentric camming elements 60, 62go down to form the plate 24 around the anvils 42, 44.

After the bends are formed in the plate 24 the four cylinders 190, 192,194, 196 for the cams 60, 62 go up to reverse the camming elements 60,62 and return the camming elements 60, 62 to the upper split bearings114. When the camming elements 60, 62 are reversed, the four cylinders130, 132, 134, 136 for the end plates 70, 72, 74, 76 go up to raise theclamping bars 120, 122, and the upper split bearings. The anvilcylinders 191 are then withdrawn to retract the retractable anvil 44.When the anvil cams 193 and cylinders 191 are withdrawn two additionalcylinders 244, 246 for ejection eject the plate 24 through the apertures270, 272 in the end plates 70, 72 at approximately four to five secondsper six inches and retract. After the ejection cylinders 244, 246 areretracted and plate 24 is removed the bending fixture 20 is ready toaccept a new plate 24 for bending. If automated for sequentialoperations, this entire operation takes no more than fifteen secondsfrom initial contact of the plate 24 to the limit switches 202, 204, 206to ejection of the prefectly formed lithographic plate 24.

In general, while I have described a specific embodiment of myinvention, it is to be understood that this is for purposes ofillustration only and that various modifications can be made within thescope of the invention as set forth by the following claims.

I claim as my invention:
 1. A web bending fixture for bending plates ofmetal having a leading edge and a trailing edge comprising:a bed tosupport the plate to be bent; at least one anvil having a bending radiusat the edge of the bed; at least one eccentric camming member having abending surface positioned relative to the anvil to bend one of theedges of the plate around the bending radius of the anvil; a fullbearing supporting each end of the eccentric camming member forrotation; a plurality of additional bearings intermediate the ends ofthe eccentric camming member within which the eccentric camming memberis rotatably contained during rotation, the additional bearings beingspaced along the length of the eccentric camming member to radiallysupport the eccentric camming member throughout its length; and meansfor rotating the eccentric camming member around the bending radius ofthe anvil, the closest point on the bending surface of the eccentriccamming member being spaced from the anvil at all times during rotationa distance equivalent to the thickness of the plate being bent.
 2. Theweb bending fixture of claim 1 wherein two anvils are provided, atopposing ends of the bed, to bend both the leading edge and the trailingedge of the plate and wherein an eccentric camming member is positionedadjacent each anvil to form both the leading edge and the trailing edgeof the plate, each eccentric camming member having a bending surface,the closest point on which is spaced from the adjacent anvil duringbending a distance equivalent to the plate being bent.
 3. The webbending fixture of claim 2 wherein one of the anvils is retractable forpurposes of removing the plate from the bed of the web bending fixture.4. The web bending fixture of claim 1 further comprising means toposition the plate on the bed of the web bending fixture.
 5. The webbending fixture of claim 4 wherein the means to position the platecomprise apertures in the bed of the web bending fixture through whichair is passed to provide an air cushion upon which the plate can rideduring positioning.
 6. The web bending fixture of claim 4 wherein themeans to position the plate comprise a plurality of limit switches todetermine when the plate is in position.
 7. The web bending fixture ofclaim 6 wherein at least three limit switches are utilized to positionthe plate on the bed of the web bending fixture.
 8. The web bendingfixture of claim 4 wherein the plate has a plurality of registrationholes prepunched in the plate before bending and wherein the means toposition the plate prior to bending comprise registration pin mechanismshaving registration pins for insertion into the registration holes. 9.The web bending fixture of claim 8 wherein at least two registration pinmechanisms are utilized to locate and fix the plate relative to tworegistration holes.
 10. The web bending fixture of claim 8 wherein atleast three registration pin mechanisms are utilized, two on one edge ofthe plate and one on the opposing edge of the plate to preciselyposition the plate relative to the bends to be made by the web bendingfixture.
 11. The web bending fixture of claim 8 further comprising:anend plate on each end of the eccentric camming member containing thefull bearings which support each end of the eccentric camming member forrotation; a header bar secured between the end plates; and wherein eachregistration pin mechanism comprises:a registration pin having a roundedtip for insertion into the registration hole; means for inserting andwithdrawing the registration pin into and out of the registration hole;a block fixed to the bed adjacent the registration hole in the plate; aset of containment fingers for straddling the registration hole abovethe plate and being slidably mounted in the block; a ramp mechanismsecured to the containment fingers slidably movable therewith andpositioned above the containment fingers; positioning means attached tothe header bar above the ramp mechanism, said header bar and positioningmeans being vertically movable so that the positioning means when moveddownwardly engages the ramp to slide it and the associated containmentfingers rearwardly away from the registration hole and edge of theplate; and biasing means attached to the block and to the containmentfingers and associated ramp to bias the fingers and associated ramptoward the edge of the plate so that when the positioning means movesupwardly the containment fingers and associated ramp move forwardlytoward the adjacent registration hole and edge of the plate.
 12. The webbending fixture of claim 1 further comprising means to secure the plateto the bed of the web bending fixture prior to bending.
 13. The webbending fixture of claim 12 wherein the means to secure the plate to thebed comprises apertures through the bed of the web bending fixturethrough which air is drawn to create a vacuum.
 14. The web bendingfixture of claim 12 wherein the means to secure the plate to the bed ofthe web bending fixture comprise clamp means to hold the plate to thebed of the web bending fixture.
 15. The web bending fixture of claim 1wherein the plurality of additional bearings are split bearingscomprising upper bearings carried by upper bearing mounts and lowerbearings carried by lower bearing mounts secured to the bed of the webbending fixture.
 16. The web bending fixture of claim 15 wherein theupper bearing mounts and lower bearing mounts are secured togetherduring the bending to provide the plurality of additional bearings, eachadditional bearing having a continuous bearing surface during thebending of the plate by the web bending fixture.
 17. The web bendingfixture of claim 16 further comprising:an end plate on each end of theeccentric camming member each end plate containing the full bearingsupporting the end of the eccentric camming member; a header bar securedbetween the end plates; a first motive means connected to the end platesto vertically move the end plates and header bar upwardly and downwardlyand wherein the upper bearing mounts are secured to the header bar sothat when the end plates and header bar is moved downwardly the upperbearing mounts and lower bearing mounts are secured together to providethe continuous bearing surfaces.
 18. The web bending fixture of claim 1wherein at least four bearings are positioned intermediate the ends ofthe eccentric bending member to support the eccentric bending memberduring bending.
 19. The web bending fixture of claim 1 wherein sixbearings are provided intermediate the ends of the eccentric bendingmember to support the eccentric bending member during bending.
 20. Theweb bending fixture of claim 1 further comprising:an end plate on eachend of the eccentric camming member; a header bar secured between theend plates; a plurality of upper split bearing mounts having upperbearing surfaces secured to the header bar; a plurality of lower splitbearing mounts having lower bearing surfaces secured to the bed; meansfor slidably attaching the end plates to the bed of the web bendingfixture; clamp means operatively secured to the header bar; first motivemeans connected to the end plates to slide the clamp means intoengagement with the plate to clamp the plate to the bed of the webbending fixture and to slide the upper split bearing mounts into asecured engagement with the lower split bearing mounts to provide theplurality of additional bearings and so that a plurality of continuousbearing surfaces are provided to support the eccentric camming memberduring rotation; and second motive means connected to the means forrotating the eccentric camming member so that a bend is formed in theedge of the plate.
 21. The web bending fixture of claim 20 wherein thefirst motive means comprises a set of cylinders, one associated witheach end plate and connected to raise and lower the end plate.
 22. Theweb bending fixture of claim 20 wherein the means for rotating theeccentric camming member comprises a rack and pinion gear on each end ofthe eccentric camming member.
 23. The web bending fixture of claim 22wherein a rack is slidably mounted on each end plate.
 24. The webbending fixture of claim 23 wherein the second motive means comprises aset of cylinders, one on each end of the eccentric camming member andmounted on each end plate and connected to each rack so that when theracks are moved they rotate the associated pinion gears.
 25. The webbending fixture of claim 20 further comprising means for retracting theanvil after a bend is formed in the plate so that the plate can beremoved from the web bending fixture.
 26. The web bending fixture ofclaim 25 wherein the anvil is slidably attached to the bed and movablebetween a bending position and a retracted position and wherein themeans for retracting the anvil comprise:a set of three verticallymovable cams positioned behind the anvil so that when in their upwardposition they slide the anvil forward to the bending position and whenin their downward position allow the anvil to retract; third motivemeans connected to the cams to move the cams up to slide the anvil tothe bending position and to move the cams down so the anvil can beretracted; and biasing means between the bed and the anvil to retractthe anvil when the cams are moved by the motive means to the downwardposition.
 27. A web bending fixture for bending plates of metal havingan image thereon and a leading edge and a trialing edge comprising:a bedto support the plate to be bent; two anvils at opposing ends of the bed,each having a bending radius at the edge of the bed; a set of twoeccentric camming members, one associated with each anvil, eacheccentric camming member having a bending surface positioned relative tothe adjacent anvil to bend one of the edges of the plate around thebending radius of the anvil; two sets of end plates, one set associatedwith each eccentric camming member to provide an end plate on each endof each of the eccentric camming members, each end plate having a fullbearing mounted therein for supporting the end of the eccentric cammingmember with which it is associated for rotation; a header bar securedbetween each of the two sets of end plates; a plurality of upper splitbearing mounts having upper bearing surfaces secured to each header bar;a plurality of lower split bearing mounts having lower bearing surfacessecured to the bed below each header bar; means for slidably attachingthe end plates to the bed of the web bending fixture in a manner thatthey can be moved upwardly and downwardly; means for positioning a plateon the bed; means for aligning the plate on the bed so that the image onthe plate is in registration with the bends to be formed in the plate;clamp means operatively secured to each header bar; a first set of fourcylinders, one connected to each end plate to vertically move the endplates downwardly so that the clamp means clamp the leading edge andtrailing edge of the plate to the bed of the web bending fixture and sothat the upper split bearing mounts are moved into a secured engagementwith the lower split bearing mounts to provide a plurality of additionalbearings intermediate the ends of each of the eccentric camming memberseach of the plurality of additional bearings having a continuous bearingsurface when secured together to support each eccentric camming memberthroughout its length during rotation; means for rotating each of theeccentric camming members around the bending radius of the adjacentanvil so that the closest point on the bending surface of each eccentriccamming member is spaced from the adjacent anvil at all times duringrotation a distance equivalent to the thickness of the plate being bent,said means for rotating the eccentric camming member comprising: a rackand pinion gear associated with each end of each eccentric cammingmember; and a second set of four cylinders, one on each end plate andconnected to the racks to slidably move each rack in a downwarddirection so that the associated pinion gears rotate the eccentriccamming members so that a bend is formed in the leading edge and thetrailing edge of the plate; and means for removing the formed plate fromthe fixture. .Iadd.
 28. A web bending fixture for bending plates ofmetal having a leading edge and trailing edge comprising:a bed tosupport the plate to be bent; at least one anvil having a bending radiusat the edge of the bed; at least one eccentric camming member having abending surface positioned relative to the anvil to bend one of theedges of the plate around the bending radius of the anvil; a fullbearing supporting each end of the eccentric camming member forrotation: at least one additional bearing intermediate the ends of theeccentric camming member within which the eccentric camming member isrotatably contained during rotation, supporting radially the eccentriccamming member intermediate its length; and means for rotating theeccentric camming member around the bending radius of the anvil, theclosest point on the bending surface of the eccentric camming memberbeing spaced from the anvil at all times during rotation a distanceequivalent to the thickness of the plate being bent. .Iaddend. .Iadd.29. The web bending fixture of claim 28 wherein the additional bearingcomprises a split bearing having an upper bearing carried by an upperbearing mount and a lower bearing carried by a lower bearing mountsecured to the bed of the web bending fixture. .Iaddend.